While I was writing a paper in NWP, I had to rebuild my Endnote database. Prior to rebuilding, all footnotes formatted perfectly. After I rebuilt, all Endnote citations (55 total) were read by Endnote as "ambiguous" and so could not be formatted. I thought this might be an Endnote problem. However, I copied the document in MS Word, and Endnote formatted it without a hitch.

Unless I'm missing something, it seems you can't rebuild an Endnote database while writing a paper in NWP.